From 57e09334cf351d1c281e4970f7a7cd9c952acbd5 Mon Sep 17 00:00:00 2001
From: Jordan Krage <jmank88@gmail.com>
Date: Sat, 26 Aug 2017 08:25:04 -0500
Subject: [PATCH] leverage reflect.MakeMapWithSize introduced in go1.9

---
 decode.go      |  6 ++----
 decode_go18.go |  9 +++++++++
 decode_go19.go | 12 ++++++++++++
 3 files changed, 23 insertions(+), 4 deletions(-)
 create mode 100644 decode_go18.go
 create mode 100644 decode_go19.go

diff --git a/decode.go b/decode.go
index e7686f9..b291e47 100644
--- a/decode.go
+++ b/decode.go
@@ -669,8 +669,7 @@ func objectIntoStruct(structPtr reflect.Value) func(*ObjectDecoder) error {
 func objectIntoMap(mapPtr reflect.Value) func(*ObjectDecoder) error {
 	return func(o *ObjectDecoder) error {
 		mapValue := mapPtr.Elem()
-		//TODO go1.9 - MakeMapWithSize
-		mapValue.Set(reflect.MakeMap(mapValue.Type()))
+		mapValue.Set(makeMap(mapValue.Type(), o.Len))
 		elemType := mapValue.Type().Elem()
 
 		for o.NextEntry() {
@@ -697,8 +696,7 @@ func objectAsInterface(o *ObjectDecoder) (interface{}, error) {
 	valType := elementTypeFor(o.ValType)
 	mapType := reflect.MapOf(stringType, valType)
 
-	//TODO go1.9 - MakeMapWithSize
-	mapValue := reflect.MakeMap(mapType)
+	mapValue := makeMap(mapType, o.Len)
 	for o.NextEntry() {
 		k, err := o.DecodeKey()
 		if err != nil {
diff --git a/decode_go18.go b/decode_go18.go
new file mode 100644
index 0000000..540ab78
--- /dev/null
+++ b/decode_go18.go
@@ -0,0 +1,9 @@
+// +build !go1.9
+
+package ubjson
+
+import "reflect"
+
+func makeMap(typ reflect.Type, _ int) reflect.Value {
+	return reflect.MakeMap(typ)
+}
diff --git a/decode_go19.go b/decode_go19.go
new file mode 100644
index 0000000..d1c818c
--- /dev/null
+++ b/decode_go19.go
@@ -0,0 +1,12 @@
+// +build go1.9
+
+package ubjson
+
+import "reflect"
+
+func makeMap(typ reflect.Type, cap int) reflect.Value {
+	if cap < 0 {
+		cap = 0
+	}
+	return reflect.MakeMapWithSize(typ, cap)
+}